1. Field of the Invention
The present invention relates to a method of and an apparatus for crushing earth and sand located in a certain depth under the ground.
2. Prior Art
Oil is drawn up, for example from oil sand or heavy oil beds which are formed in layers under the ground. The oil sand bed which is exposed on the ground can be easily excavated, and oil is extracted from the oil sand thus collected. When the oil sand bed is located relatively deep under the ground, a certain area of the oil sand bed is crushed and oil to be extracted is separated from the sand generally by an electrically preheating system in which AC current is conducted in the crushed area filled with salt water or by a steam heating system in which steam is introduced under pressure into the crushed area. In these cases, it is desired to crush the oil sand bed as widely as possible for effectively drawing up a maximum amount of the oil. Furthermore, as the oil sand bed expands in the lateral or transverse direction in comparison with the vertical direction, it desired to extend the crushing in the lateral direction as far as possible.
There has been proposed a method of forming a cylindrically crushed area under the ground for hardening a foundation or driving a concrete pile by inserting a pipe carrying a drill head into a hole bored in the earth, injecting water at a high speed from nozzles directed in the lateral direction of the drill head, and rotatingly moving the pipe upwardly, as is well known in the prior art as exemplified in Japanese Patent Publication No. 54-41001, U.S. Pat. Nos. 404,758 and 4,084,648 and Japanese Patent Publication No. 57/055849. However, because water jet has a limited path length, such a method is useful only to crush a cylindrical area of radius 1 m at the utmost, when it applied for crushing, for example, an oil sand bed. Consequently, many holes must be bored in the earth to get a crushed area spreading laterally. When the oil sand bed lies, for example, 500 m below the surface of the earth, many holes must be quite uneconomical bored to that depth.